Development of a method for recovery of 233U from thorium oxalate cake in reconversion step of reprocessing of irradiated thorium rods

A method is developed for the selective leaching of ²³³U from a thorium oxalate cake. The leaching capacity of ammonium carbonate and nitric acid have been investigated, showing that (NH₄)₂CO₃ leads to higher recovery. The maximum leaching efficiency is obtained using 0.5% ammonium carbonate, with a minimal thorium pick-up. A uranium recovery of 94% is obtained after three consecutive contact experiments in carbonate media, with minimal thorium uptake in the leachate. This process was applied to an actual plant stream, allowing the reduction of the ²³³U -activity from 5.64 to 0.3 Ci/g of thorium oxalate cake.     

Novel Carbon–Carbon Bond Formation between N‐Methyl‐3‐phenyl‐3‐hydroxypropylamine and Cresols Catalyzed by p‐Toluenesulphonic Acid

The p‐toluenesulphonic acid–catalyzed reaction between appropriate cresols and N‐methyl‐3‐phenyl‐3‐hydroxypropylamine in refluxing toluene resulted in the formation of o‐substituted phenol derivatives by an aromatic nucleophilic substitution reaction.     

Drop calorimetric measurements on a versatile monazite phase loaded with simulated radioactive waste

Monazite is one of the candidate ceramic matrices for the immobilization of high level radioactive waste (HLW) from the reprocessing of spent nuclear fuel. The monazite phase, Ce_0.8Ca_0.2PO₄, can accommodate cations of different valences due to the mixed valence state (+3 and +4) of Ce in this compound, by facilitating the oxidation and reduction of the Ce³⁺ and Ce⁴⁺ as required by the in-coming cation. This will assist in accommodating HLW of different compositions in the monazite crystal structure even if the average valence of the HLW elements is other than 3. Therefore, the monazite phase, Ce_0.8Ca_0.2PO₄, can be a versatile host for the immobilization of HLW. The enthalpy increment and heat capacity of this versatile monazite phase and a simulated waste form based on it with 20 mass% HLW oxides were measured by drop calorimetry in the temperature range from 373 to 873 K, and the results are compared with those measured for CePO₄.     

A weak immersion relation on graphs and its applications

Weak immersion is a generalization of the immersion relation defined by Nash-Williams. A graph H is said to be weakly immersed in a graph G if H can be obtained from G by a sequence of these three operations: taking a subgraph, splitting a vertex, and lifting a pair of adjacent edges. The weak immersion relation has the useful property that finite graphs are well-quasi-ordered by it, which also holds for graphs with some vertices designated as terminals. As a result, any family of finite graphs that is closed under weak immersion can be characterized by a finite number of minimal forbidden graphs called obstructions. Weak immersion offers two advantages over immersion for practical applications. First, although closure under weak immersion implies closure under immersion, families can have significantly fewer obstructions under weak immersion. Hence weak immersion can provide simpler characterizations for closed families. Examples include graphs of bounded cutwidth and graphs of bounded multiway cutsize. The difference in the number of obstructions is at least exponential in the cutwidth and in the square-root of the multiway cutsize. Second, for every fixed graph H, there is a polynomial-time algorithm to decide whether H is weakly immersed in an input graph G. Consequently, there is a polynomial-time membership test for any family that is closed under weak immersion. In principle, testing for weak immersion is as fast as testing for immersion. Thus the simpler characterization provided by weak immersion may lead to faster membership algorithms.     

Thermal expansion and heat capacity measurements on Ba10?xCsx(PO4)6Cl2?δ, (x?=?0, 0.5) chloroapatites synthesized by sonochemical process

Ba_10−x Cs _x (PO₄)₆Cl₂, (x = 0, 0.5) chloroapatite ceramics were prepared by sonochemical method of synthesis. The measured room temperature lattice parameters of Ba₁₀ (PO₄)₆Cl₂ and Ba_9.5Cs_0.5 (PO₄)₆Cl_2−δ are practically the same; that is, a = 10.26 (8), c = 7.65 (7) and a = 10.27 (7), c = 7.65 (5), respectively. Heat capacity measurements were carried out on these materials by differential scanning calorimetry (DSC) in the temperature range 298–800 K. The heat capacity values of Ba_9.5Cs_0.5(PO₄)₆Cl_2−δ are found to be slightly higher at all temperatures than those of Ba₁₀(PO₄)₆Cl₂. From the heat capacity data, other thermodynamic functions such as enthalpy and entropy increments were computed. The heat capacity values of Ba₁₀(PO₄)₆Cl₂ and Ba_9.5Cs_0.5(PO₄)₆Cl_2−δ at 298 K are 0.3912 and 0.4310 J K⁻¹ g⁻¹, respectively. Thermal expansion property of the doped and undoped barium chloroapatites was measured by using a home built dilatometer which uses LVDT as displacement sensor. The bulk thermal expansion of Ba₁₀(PO₄)Cl₂ and Ba_9.5Cs_0.5(PO₄)Cl_2−δ is observed to be about 0.9% in the temperature range of 298–973 K.     

Phytochemical constituents from dietary plant Citrus hystrix

Chemical investigation of the fruit peel of dietary plant Citrus hystrix offered two new flavones 5,6,4′-trihydroxypyranoflavone I and 5,4′-dimethyl-6-prenylpyranoflavone XIII besides 11 known compounds. The structures of all compounds were elucidated with the aid of suitable analytical methods like 1D, 2D-NMR, mass and single crystal X-ray analysis. An X-ray crystal study of compound II was done for the first time and the compounds I–VI, XI and XII are hitherto not reported from this plant. Biological studies revealed that compound I found to have a good antidiabetic and antiacetylcholinesterase activities meanwhile compounds II, III and V showed a significant free radical scavenging ability as well as antioxidant capacity. In addition, compounds I, IV, V and VI showed cytotoxicity against U87, A549 and MCF-7 cells. Overall, the new compound I showed valuable bioactive properties. Due to insufficient quantity of compound XIII, biological studies were not done.     

Dielectric properties of CaCu3Ti4O12–silicone resin composites

CaCu₃Ti₄O₁₂ (CCTO)–silicone resin composites with various CCTO volume fractions were prepared. Relatively high dielectric constant (ε=119) and low loss (tanδ=0.35) of the composites with CCTO volume fraction of 0.9 were observed. Two theoretical models were employed to predict the dielectric constant of these composites; the dielectric constant obtained via the Maxwell–Garnett model was in close agreement with the experimental data. The dielectric constant of CCTO–silicone resin composites showed a weak frequency dependence at the measuring frequency range and the loss tangent apparently decreases with increase in frequency.     

Piezoelectric and pyroelectric properties of lead lanthanum zirconate titanate (PLZT) ceramics prepared by sol gel derived nano powders

Lanthanum modified PZT (PLZT) ceramics were prepared with nano powders obtained by the sol gel method and its piezoelectric and pyroelectric behaviour was studied. The piezoelectric properties of the sol gel derived ceramics were compared with the ones prepared by the conventional oxide route. It was found that although the figures of merit of the sol gel derived ones were slightly better (10–15% increase), because of its higher density with respect to conventional ones. The pyroelectric properties of PLZT needs special mention because of its high detectivity and low noise levels. The results are tabulated in the paper and it indicates great figures of merit.